With the continuous progress of technologies, displays have evolved from traditional displays to liquid crystal displays or even touch displays. General liquid crystal displays need at least an input device, such as keyboard or mouse, to control the pointer on displays and perform clicking or typing operations. For touch displays, no mouse is required. A user can control the pointer and type by touching displays directly. Thanks to the omission of input devices, the space occupied by computers is reduced; the location for placing computers will be less limited. In addition, due to their simple operational methods, touch displays are easier and friendlier for the elderly and children.
Nonetheless, no matter resistive or capacitive touch displays, many components, including touch panels and touch control chips, are required. Unfortunately, the components described above are costly. Besides, modern computers have already equipped with displays. If the original undamaged displays are replaced directly by touch displays, the cost will be expensive; it is also wasting resources and against the trend of environmental protection. Thereby, there is an add-on optical touch screen in the market. The add-on optical touch screen is disposed on a current liquid crystal display and thus enabling a general liquid crystal to have touch functions.
The size of the add-on optical touch screen described above is fixed and unadjustable, making it applicable only to displays of a single size. As the display is changed to another size, a new add-on optical touch screen has to be purchased. Moreover, because the size of current add-on optical touch screens becomes larger as the display size increases, they will occupy a large space for storage.